1. Field of the Invention
The present invention relates to a non-contact type potentiometer, an actuator, a vehicle mounted radar device, and an automobile drive control system. More specifically, the present invention relates to a non-contact type potentiometer that uses a magnetic detection element to detect a rotational angle of a rotary shaft, and an actuator, a vehicle mounted radar device, and an automobile drive control system that employs such non-contact type potentiometer.
2. Description of the Related Art
Potentiometers that use a magnetic detection element such as a Hall element or other similar element to detect a rotational angle of a rotary shaft are known. By using a magnetic detection element, the angle in which the rotary shaft has been rotated can be detected without contact between a detection means and a rotor. Therefore, non-contact type potentiometers that use a magnetic detection element have a longer life than potentiometers that use a contact type rotor position detecting means such as a brush or the like, because the contact type of potentiometers have problems associated with friction caused by contact between the detecting means and the rotor.
In conventional non-contact type potentiometers that employ a Hall element to detect the intensity of the magnetic field generated by a magnet, the intensity of the magnetic field surrounding the Hall element can be altered by altering the distance between the magnet and the Hall element in accordance with the rotation of a rotary shaft. For example, if a magnet is fixed on the outer circumference of a rotor having a rotary shaft and a Hall element is mounted on a stationary member, the distance between the magnet and the Hall element will vary when the rotor is rotated. Thus, based upon the output signals from the Hall element, the angle of rotation of the rotor can be determined.
However, because the lines of magnetic force extend from the magnet such that they diffuse away therefrom, the intensity of the magnetic field around the Hall element is reduced when the distance between the magnet and the Hall element is changed. As a result, the conventional potentiometers described above cannot detect the angle in which a rotor has been rotated with a high degree of precision.
In addition, if the magnet is fixed on the rotor, the intensity and direction of the magnetic field around the Hall element is complexly changed by the rotation of the rotor, therefore, the output signal from the Hall element cannot be directly correlated with the actual angle in which the rotary shaft has been rotated.
It is therefore an object of the present invention is to improve the precision with which a non-contact type potentiometer detects an angle at which a rotary shaft has been rotated, without increasing the cost thereof.
It is another object of the present invention to provide a highly reliable actuator that employs a non-contact type potentiometer capable of detecting an angle in which a rotary shaft has been rotated with a high degree of precision.
It is yet another object of the present invention to provide a safe automobile drive observation system that employs a non-contact type potentiometer capable of detecting both an angle in which a rotary shaft has been rotated, and obstructions in the road, with a high degree of precision.
It is yet another object of the present invention to provide a safe automobile drive control system that employs a non-contact potentiometer that is capable of both detecting an angle in which a rotary shaft has been rotated with a high degree of precision, and accurately detecting the operation of the accelerator and/or brakes by the driver and thereby control the acceleration and deceleration of the automobile.
The present invention is a non-contact type potentiometer in which a pair of planar magnets are disposed in an opposing and parallel spaced relationship on a stationary member, with the polarities of the magnets being arranged such that approximately parallel magnetic fields are formed around a magnetic detection element that is fixed on a support shaft that can freely rotate relative to the stationary member.
An angle in which a rotary shaft has been rotated can be detected with a high degree of precision because the magnetic detection element is positioned in approximately parallel magnetic fields. Thus, there is very little variation in the magnetic fields, even if the magnetic detection element rotates together with the support shaft.
In addition, the safety and reliability of actuators, vehicle mounted radar devices, and automobile drive control systems can be improved by using this type of non-contact type potentiometer to detect rotational angles of rotary shafts employed in these devices.
These and other objects, features, aspects and advantages of the present invention will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses a preferred embodiment of the present invention.